A combined Raman scattering and Rutherford backscattering (RBS) study on both polycrystalline and single-crystalline cubic (3C-) SiC thin films grown on (100) Si by vertical chemical vapor deposition (V-CVD) is presented. The V-CVD growth was performed using a new system with a vertical reactor and a rotating susceptor. The Raman spectra show the presence of cubic-phase transverse optical (TO) and longitudinal optical (LO) phonon modes at the Gamma point which are characteristic of both poly- and single-crystalline films, but are distinguished by different intensity ratios and polarization. There also exist weak shoulders around the LO(Gamma) band due to the 6H polytype and defects. The variations of the above features with the growth parameters, film thickness and laser excitations are studied. Two quantitative intensity ratios between different phonon modes are introduced and used to assess the 3C-SiC/Si structures. RES was used to determine the Si:C stoichiometric ratio and film thickness for films thinner than 1 mu m. Ion channeling data indicate excellent crystallinity of the 3C-SiC single crystalline films grown on Si by the V-CVD technique. The related physical phenomena and growth mechanisms of the vertical CVD technique for the growth of SiC films and devices are discussed.